1. Field of the Invention
The present invention relates generally to a synthetic resin bag. More particularly, the present invention relates to a bag used for packing and storing grain or animal feed, especially powdered feed, feed containing fish oil of high permeation, feed containing much fat and moisture.
2. Description of the Related Art
It is well known that a burlap bag is used chiefly for carrying or storing items, for example, feed for domestic animals such as dog, chicken, cat and fish, or grain such as rice, barley, wheat and corn. In the past, a storage bag for grain or feed was made mainly of paper. The paper bag is, however, easily damaged in use by water or moisture. Furthermore, since the paper bag is not waterproof, contents of the bag can be badly changed in quality or easily lose their freshness by water penetrated into the paper bag. Additionally, in case of packing feed full of fat or oil, such fat or oil is unfavorably absorbed into paper.
A later paper bag is therefore reinforced with additional agents to prevent penetration by water and absorption of fat or oil. This type of a paper bag is illustrated in FIG. 1. Referring to FIG. 1, a paper bag 100 is composed of a dual paper structure, i.e., an outer paper layer 102 and an inner paper layer 103. In order to reinforce the paper layers 102 and 103, a layer 104 of polyethylene (PE) resin coats the inner layer 103. Also, a printed portion P partially covers the outer layer 102. The printed portion P is a set of certain figures or words directly printed on the outer layer 102, or alternatively a synthetic resin film printed with figures or words and adhering to the outer layer 102.
Upper and lower ends of the paper bag 100 are fastened by stitching, thereby forming sealing portions 105 and 105′. The upper sealing portion 105′ has a stitching thread 106 and an unstitching thread 107. The unstitching thread 107 facilitates the opening of the bag 100.
Unfortunately, the above-described conventional paper bag 100 has some drawbacks. First, since the outer and inner paper layers 102 and 103, and the PE coating layer 104 are different in material, the paper bag 100 is difficult to recycle and cost-ineffective. Furthermore, since the outer paper layer 103 is still exposed to a damp environment, the strength of the paper bag 100 tends toward lowering over time by moisture in the air. This often causes a damage of the paper bag 100 while packed or conveyed. Additionally, the conventional paper bag 100 is prone to slip and fall due to a low sliding friction while stacked.
Moreover, if powdered feed is packed in the paper bag 100, powdered feed is apt to solidify by exposure to the ventilation of air. To solve such a problem, there is a case where the following steps are added, namely, inserting a vinyl bag into the paper bag, putting powdered feed in the vinyl bag, and tying up the upper end of the vinyl bag with a string. This solution, however, leads to the increases of manufacturing cost and working hours.